Antimicrobial Medical Devices Containing Chlorhexidine Free Base and Salt

ABSTRACT

The present disclosure invention relates to medical devices treated with a solution comprising one or more solvents and a combination of chlorhexidine free base and a water-soluble chlorhexidine salt in a weight/weight ratio of between about 1:1 to about 1:5, preferably about 1:1.

1.0 INTRODUCTION

The present invention relates to medical devices treated with a solutioncomprising a combination of chlorhexidine free base and a water-solublechlorhexidine salt, in a ratio that facilitates chlorhexidine uptake bythe devices and hence improves antimicrobial effectiveness.

2.0 BACKGROUND OF THE INVENTION

Whenever a medical device comes in contact with a patient, a risk ofinfection is created. Thus, a contaminated examination glove, tonguedepressor, or stethoscope could transmit infection. The risk ofinfection dramatically increases for invasive medical devices, such asintravenous catheters, arterial grafts, intrathecal or intracerebralshunts and prosthetic devices, which not only are, themselves, inintimate contact with body tissues and fluids, but also create a portalof entry for pathogens.

Catheter related infections, especially blood stream infections, areassociated with increased morbidity (10 to 20 percent), prolongedhospitalization (by a period having a mean of seven days), and increasedmedical costs (approximately $6,000 per hospitalization). According to asurvey of intensive care units from 1986 through 1990 by the NationalNosocomial Infection Surveillance System, the rate of catheter-relatedblood stream infections ranged from 2.1 to 30.2 per 1,000 catheter-days.Infections associated with central venous catheters have been reportedto result from the transcutaneous migration of the pathogens from theinsertion site with the eventual colonization of the catheter tip. Inaddition, intraluminal colonization has been suggested to result fromcontaminated hubs and infusates that contribute to catheter relatedblood stream infections. The longer the duration of catheterization, thegreater the susceptibility to either luminal or outer surfacecolonization of catheters. Even for short term use of catheters,infections have been reported due to contamination of the insertionsites.

A number of methods for reducing the risk of infection have beendeveloped which incorporate anti-infective agents into medical devices.Such devices desirably provide effective levels of anti-infective agentduring the period that the device is being used. Sustained release maybe problematic to achieve, in that a mechanism for dispensinganti-infective agent over a prolonged period of time may be required,and the incorporation of sufficient amounts of anti-infective agent mayadversely affect the surface characteristics of the device. Thedifficulties encountered in providing effective antimicrobial protectionincrease with the development of drug-resistant pathogens.

One potential solution to these problems is the use of a synergisticcombination of anti-infective agents that requires relatively lowconcentrations of individual anti-infective agents which may havediffering patterns of bioavailability. For example, WO 97/25085 relatesto medical devices comprising synergistic combinations of chlorhexidineand triclosan. U.S. Pat. Nos. 5,616,338 and 5,019,096 relate toinfection resistant medical devices comprising synergistic combinationsof a silver salt, a biguanide (such as chlorhexidine) and a polymericcomponent that forms a matrix to provide a sustained release of thesilver salt and biguanide.

U.S. Pat. Nos. 5,165,952 and 5,451,424 relate to medical articles withchlorhexidine both coated on and bulk distributed throughout the medicalarticles. When chlorhexidine is bulk distributed it adversely affectscertain characteristics of the device such as tensile strength, and thehigh temperatures needed for extension of plastics such as polyurethanemay damage the chlorhexidine.

U.S. Pat. No. 5,089,205 relates to incorporation of chlorhexidine freebase or one of its salts in a medical device such as a glove by both adistribution or dipping process.

Chlorhexidine is a broad spectrum antimicrobial agent and has been usedas an antiseptic for several decades with minimal risk of developingresistant microbes. When relatively soluble chlorhexidine salts, such aschlorhexidine acetate, were used to impregnate catheters, the releasewas undesirably rapid. The duration of the antimicrobial efficacy ofmedical devices impregnated with chlorhexidine salts, such aschlorhexidine acetate, is short lived. Chlorhexidine free base is notsoluble in water or alcohol and cannot be impregnated in sufficientamounts because of low solubility in a solvent system.

In contrast to the present invention, none of the above-cited referencesteach medical articles treated with a solution comprising a combinationof chlorhexidine free base and a water-soluble chlorhexidine salt, atparticular ratios, which provide improved antimicrobial effectivenessthrough an increased uptake of chlorhexidine into the medical device,increased retention of chlorhexidine in the medical device and prolongedrelease of chlorhexidine from the medical device, while utilizingrelatively low levels of chlorhexidine,

3.0 SUMMARY OF THE INVENTION

The present invention relates to medical devices treated with a solutioncomprising one or more solvents and a combination of chlorhexidine freebase and a water-soluble chlorhexidine salt, in a weight/weight ratio ofbetween about 1:1 to about 1:5 (inclusive), preferably about 1:1 ofchlorhexidine free base to chlorhexidine salt. The invention furtherrelates to methods of preparing medical devices by exposing them, inwhole or in part, to a solution comprising one or more solvents and theabove-recited combinations of chlorhexidine free base and chlorhexidinesalt.

This invention is based, at least in part, on the discovery that devicestreated with combinations of chlorhexidine free base and a water-solublechlorhexidine salt exhibit improved antimicrobial effectiveness due toincreased uptake of chlorhexidine into the medical device, increasedretention of chlorhexidine in the medical device, and prolonged releaseof chlorhexidine while utilizing relatively low levels of chlorhexidine,and, in certain non-limiting embodiments, in the absence of agents otherthan chlorhexidine. In particular, while it had been previously foundthat triclosan can be particularly useful when used in conjunction withchlorhexidine free base, it has been further discovered that medicalarticles having suitable antimicrobial properties may be prepared,according to the present invention, without the use of triclosan.Therefore, in particular embodiments, medical articles according to thepresent invention offer the advantage of preventing or inhibitinginfection while avoiding undesirable adverse reactions to antimicrobialagents other than chlorhexidine by allergic individuals.

4.0 DETAILED DESCRIPTION OF THE INVENTION

The present invention provides for medical articles treated with asolution comprising one or more solvents and a combination ofchlorhexidine free base (“CHX”) and a water-soluble chlorhexidine salt,and further provides for methods of preparing medical devices byexposing the device, in whole or in part, to said solution.

While not being bound or limited by any particular theory, it isbelieved that the combination of CHX and water-soluble chlorhexidinesalt forms a soluble complex. This would explain the increased uptake ofchlorhexidine into the medical device, increased retention ofchlorhexidine in the medical device, and increased sustained release ofchlorhexidine from the medical device while utilizing relatively lowlevels of chlorhexidine in the absence of agents other thanchlorhexidine.

The following are definitions of terms used herein unless otherwiseindicated:

Water soluble chlorhexidine salts have a solubility of at least about2.0 grams per 100 ml in water at 20° C. Examples of water solublechlorhexidine salts include chlorhexidine diacetate (also referred toherein as chlorhexidine acetate, or “CHA”) and chlorhexidine digluconate(or “CHG”) with CHA being preferred.

The terms “medical article” and “medical device” are usedinterchangeably herein. Medical articles that may be treated accordingto the invention are either fabricated from and/or coated or treatedwith biomedical polymer (and hence may be referred to as “polymericmedical articles”) and include, but are not limited to, cathetersincluding urinary catheters and vascular catheters (e.g., peripheral andcentral vascular catheters), wound drainage tubes, arterial grafts, softtissue patches (such as polytetrafluoroethylene (PTFE) soft tissuepatches), gloves, condoms, shunts, stents, tracheal catheters, wounddressings, sutures, guide wires and prosthetic devices (e.g., heartvalves and LVADs). Vascular catheters which may be prepared according tothe present invention include, but are not limited to, single andmultiple lumen central venous catheters, peripherally inserted centralvenous catheters, emergency infusion catheters, percutaneous sheathintroducer systems and thermodilution catheters, including the hubs andports of such vascular catheters. The present invention may be furtherapplied to medical articles that have been prepared according to U.S.Pat. Nos. 5,616,338 and 5,019,096 by Fox, Jr. et al. and U.S. Pat. No.5,772,640 by Modak et al.

The term “hydrophilic polymeric medical article” is a medical articlefabricated from a hydrophilic polymer. As used herein, “hydrophilicpolymer” refers to polymers that have a water absorption greater than0.6 percent by weight (and, in preferred embodiments, less than 2percent by weight; as measured by a 24 hour immersion in distilledwater, as described in ASTM Designation D570-81) including, but notlimited to biomedical polyurethanes (e.g., ether-based polyurethanes andester-based polyurethanes, as set forth in Faker, 1987, in ControlledRelease of Biologically Active Agents, John Wiley and Sons, pp. 175-177and Lelah and Cooper, 1986, Polyurethanes in Medicine, CRC Press, Inc.,Fla. pp. 57-67; polyurethanes comprising substantially aliphaticbackbones such as Tecoflex™ 93A; polyurethanes comprising substantiallyaromatic backbones such as Tecothane™; and Pellethane™), polylacticacid, polyglycolic acid, natural rubber latex, and gauze orwater-absorbent fabric, including cotton gauze and silk suture material.

The term “hydrophobic polymeric medical article” is a medical articlefabricated from a hydrophobic polymer. As used herein, “hydrophobicpolymer” refers to a polymer that has a water absorption of less than0.6% (w/w) and includes, but is not limited to, silicone polymers suchas biomedical silicones (e.g., Silastic Type A) or elastomers (e.g., asset forth in Baker, 1987, in Controlled Release of Biologically ActiveAgents, John Wiley and Sons, pp. 156-162), Dacron, PTFE (also “Teflon”),expanded PTFE, polyvinyl chloride (PVC), cellulose acetate,polycarbonate, and copolymers such as silicone-polyurethane copolymers(e.g., PTUE 203 and PTUE 205 polyurethane-silicone interpenetratingpolymer).

The terms “treat”, “treated”, “treating”, etc., as used herein, refer tocoating, impregnating, or coating and impregnating a medical articlewith anti-infective agent. Medical articles are “treated” by exposingthem, for an effective period of time, to a treatment solution, where an“effective period of time” is that period of time sufficient tointroduce anti-infective qualities of the anti-infective agent to thearticles. Medical articles may be dipped, soaked, or otherwise have asurface coated. The term “dipped” suggests briefer exposure to thetreatment solution relative to “soaking,” and preferably is for a periodof time less than fifteen minutes.

Percentages recited herein refer to weight/volume (w/v), except asindicated otherwise (e.g., volume/volume or “v/v”).

The term “CFU” means colony forming unit.

The term “about” indicates a variation within 20 percent.

The present invention provides for medical articles treated with asolution comprising one or more solvents and a combination of CHX and awater-soluble chlorhexidine salt, in a weight/weight ratio of betweenabout 1:1 and 1:5, preferably about 1:1. Such medical articles includehydrophilic polymeric medical articles as well as hydrophobic polymericmedical articles fabricated from and/or coated or treated with such abiomedical polymer. In addition, the present invention may be applied tomedical articles that have been prepared according to U.S. Pat. Nos.5,616,338 and 5,019,096 by Fox, Jr. et al. and U.S. Pat. No. 5,772,640by Modak et al. Such one or more solvents may be selected from the groupconsisting of water, reagent alcohol, and tetrahydrofuran (“THF”),dimethylsulfoxide, dimethylformamide, N-methyl-2-pyrrolidone, andmixtures thereof.

In a specific non-limiting embodiment, the treatment solution comprisesCHX—CHA in a weight/weight ratio between about 1:1 and about 1:5,preferably about 1:1 of CHX to CHA.

The present invention further provides, in a non-limiting embodiment,for methods of preparing medical devices by treating the device, inwhole or in part, with a solution comprising one or more solvents and acomplex formed by synergistic combinations of chlorhexidine free baseand chlorhexidine acetate.

In non-limiting embodiments, medical articles may be treated with asolution comprising the steps of (i) placing the medical article in asolution comprising (a) a solvent selected from the group consisting ofwater, reagent alcohol, THF, dimethylsulfoxide, dimethylformamide,N-methyl-2-pyrrolidone, and mixtures thereof and (b) a mixture of CHXand a water-soluble chlorhexidine salt, preferably CHA, preferably in aweight/weight ratio of between about 1:1 and about 1:5; (ii) soaking themedical article in the solution for an effective period of time to allowthe medical article to swell and to incorporate the anti-infectiveagents; (iii) removing the medical article from the solution; and (iv)drying the medical article.

Medical articles prepared according to the invention may be treated onan external surface, internal surface, or both. For example, and not byway of limitation, where the medical article is a catheter having alumen, the internal (i.e., luminal) surface and/or external surface ofthe catheter may be treated together or separately according to theinvention. An open-ended catheter may be placed in a treatment solutionsuch that the internal and external surfaces are exposed to thetreatment solution. Alternatively, the ends of the catheter may besealed before being placed in the treatment solution so that only theexternal surface is exposed to the treatment solution. Alternatively,only the internal surface may be exposed to the treatment solution ifthe solution is pushed, pulled or allowed to pass through and/or fillthe lumen without immersing the catheter in the treatment solution.

In specific non-limiting embodiments, a catheter having a lumen may betreated with a solution comprising the steps of (i) exposing the lumenof the catheter to a solution comprising (a) a solvent selected from thegroup consisting of water, alcohol, THF, dimethylsulfoxide,dimethylformamide, N-methyl-2-pyrrolidone, and mixtures thereof and (b)a mixture of CHX and a water-soluble chlorhexidine salt, preferably CHA,preferably in a molar ratio of between about 1:1 and about 1:5; (ii)filling the lumen of the catheter with the solution by pushing, pulling,or allowing passage of the solution into the lumen for an effectiveperiod of time to allow the material surrounding the lumen of thecatheter to swell and to incorporate the chlorhexidine; (iii) removingthe solution from the lumen of the catheter; and (iv) drying thecatheter.

In the foregoing methods, the duration of exposure of the medicalarticle or portion thereof to the treatment solution may preferably, butnot by limitation, be ten seconds to one hour. The duration of exposureof the lumen of a catheter may preferably, but not by limitation, be tenseconds to two minutes. Longer periods of exposure may be used providedthat undesirable deterioration of the medical article does not occur.

The treatment solutions may optionally further comprise (i) an organicacid, at a concentration of between about 0.1 and about 5 percent,preferably between about 0.1 and about 2 percent; (ii) ananti-inflammatory agent, at a concentration of between about 0.1 andabout 5 percent, preferably between about 0.1 and about 1 percent;and/or (iii) a hydrogel at a concentration of between about 0.5 to about10 percent, preferably between about I and about 5 percent.

5.0 WORKING EXAMPLES

The following methods were used in performing experiments discussed inthe following examples, unless indicated otherwise:

Method of Treatment of a Medical Article with Solution. The medicalarticle was treated by exposing the entire medical article, or a portionthereof, to a solution containing CHA alone, CHX alone or the CHX—CHAcombination in various amounts in a solvent system. The medical article,or a portion thereof, was exposed by soaking the article in the solutionfor 100 seconds before removing the article from the solution. Forarticles, such as catheters, having an internal lumen, the solution waspushed into the lumen and allowed to remain for 100 seconds beforeremoval.

Method of Determining Drug Uptake. The amount of drug uptake into thetreated polymeric medical articles was determined using aspectrophotometric method after extraction in alcohol.

Method of Determining Long Term Antimicrobial Efficacy in CatheterLumen. In order to determine the duration of antimicrobial efficacy incatheter lumens exposed to treatment solutions, catheters were perfusedfor 7 days using the following continuous perfusion model. The distallumens of catheters were connected to a peristaltic pump in a closedloop, wherein 1.5 L of 10% (v/v) trypticase soy broth in saline wasconstantly perfused by recycling it through each catheter lumen at arate of 83 ml/hr for 7 days. On the eighth day the catheters weredisconnected and used for evaluation of bacterial adherence.

Method of Evaluating Microbial Adherence to a Catheter Lumen. Afterperfusion of catheters for 7 days as set forth above, the distal lumensof each catheter were filled with a 10⁸ CFU/ml culture of bacteria oryeast. In the case of exposure to E. aerogenes, P. aeruginosa and C.albicans, cultures containing 10⁶ CFU/ml were used. The ends of thecatheters were heat sealed and the catheters were incubated for 24 hoursin an orbital shaker at 37° C. After 24 hours, the lock cultures werecollected from the lumen and subcultured after serial dilution usingagent inactivating media. The outer surface of the whole catheter wassterilized by wiping the outer surface with an alcohol swab. Thereafter,the lumens were flushed with 20 ml trypticase soy broth to removenon-adherent bacteria. The body of the catheters were subdivided into 2cm segments, which were further cut into 2 mm subsegments. Thesubsegments were placed in 4.0 ml agent inactivating media and sonicatedin a 4° C. water bath using an Astrasan Sonicator (Model 9T) at 60KHertz. Thereafter, 0.5 ml of the extract was then subcultured on atrypticase soy agar plate and incubated at 37° C. for 24 hours. Colonycounts were then determined.

Method of Evaluating Bacterial Adherence to PTFE Soft Tissue PatchDisks. Polytetrafluoroethylene (PTFE) disks were soaked and agitated in3.0 ml of media containing 50% (v/v) bovine adult serum and 50% (v/v)trypticase soy broth. The media was changed on days 1, 2 and 4. On thefourth day, 10⁵ CFU/ml of bacteria was added to the media. On the fifthclay, the disks were removed, rinsed and rolled on drug inactivatingagar. The plates were then incubated for 24 hours at 37° C. Colonycounts were determined thereafter.

Method of Determining Zones of Inhibition. Zones of inhibition weremeasured by seeding a specified amount of bacteria onto a trypticase soyagar plate. Then, three units of a specified amount of medical articlewere placed on the plate. The plates were incubated at 37° C. for 24hours. The zones of inhibition were then measured for Day 1. To measurethe zones of inhibition on Day 2 and subsequent days, the units ofmedical article were transferred onto a fresh plate of similarlyprepared agar, incubated at 37° C. for 24 hours and colony-free zoneswere measured.

5.1 EXAMPLE Polyurethane Central Venous Catheters

Polyurethane central venous catheters, which are hydrophilic polymericmedical articles, were separated into three otherwise identical groupsof catheters and separately treated with a solution that either (i)contained no antimicrobial agents; (ii) contained CHA alone, or (iii)contained a combination of CHX and CHA (“CHX—CHA”) in accordance withthe present invention. In particular, the luminal surfaces of thecatheters were separately treated with one of the following solutions:

(1) a solvent system of 80% (v/v) reagent alcohol and 20% (v/v) THF withno antimicrobial agents;

(2) 2.4% CHA in a solvent system of 80% (v/v) reagent alcohol and 20%(v/v) THF; and

(3) 1.2% CHX and 1.2% CHA in a solvent system of 80% (v/v) reagentalcohol and 20% (v/v) THF.

The solution was exposed to the luminal surface of the catheter bypushing the solution into the lumen and allowing the solution to remainin the lumen for 100 seconds. Thereafter, the solution was removed, andthe distal lumens of the catheters were connected to a peristaltic pumpin a closed loop, wherein 1.5 L of 10% trypticase soy broth in salinewas constantly perfused by recycling it through each catheter lumen at arate of 83 ml/hr for 7 days, according to the continuous perfusionmethod discussed above. On the eighth day the catheters weredisconnected and the ability of bacteria to adhere to the lumens wastested as follows.

The distal lumens of each of the three groups of catheters wereseparately filled with 8×10⁸ CFU/ml culture of S. epidermidis. The endsof the catheters were heat sealed and the catheters were incubated for24 hours in an orbital shaker at 37° C. After 24 hours, the lockcultures were collected from the lumen and subcultured after serialdilution using agent inactivating media. The outer surface of the wholecatheter was sterilized by wiping the outer surface with an alcoholswab. Thereafter, the lumens were flushed with 20 ml trypticase soybroth to remove non-adherent bacteria. The bodies of the catheters weresubdivided into 2 cm segments, which were further cut into 2 mmsubsegments. The subsegments were placed in 4.0 ml agent inactivatingmedia and sonicated in a 4° C. water bath using an Astrasan Sonicator(Model 9T) at 60 KHertz. Thereafter, 0.5 ml of the extract was thensubcultured on a trypticase soy agar plate and incubated at 37° C. for24 hours. Colony counts were then determined and are shown below inTable 1.

TABLE 1 Bacterial Adherence of S. epidermidis Solution (CFU/cm) 80%(v/v) reagent alcohol + 2.2 × 10⁴ 20% (v/v) THF 2.4% CHA in   3 × 10²80% (v/v) reagent alcohol + 20% (v/v) THF 1.2% CHX + 2 1.2% CHA in 80%(v/v) reagent alcohol + 20% (v/v) THF

The luminal surfaces of catheters were also tested according to theabove described techniques to evaluate the adherence of a wide varietyof organisms. The luminal surfaces of catheters were separately treatedwith the following solutions:

(1) a solvent system of 80% (v/v) reagent alcohol and 20% (v/v) THF withno antimicrobial agents; and

(2) 1.2% CHX and 1.2% CHA in a solvent system of 80% (v/v) reagentalcohol and 20% (v/v) THF.

The luminal surfaces were exposed to the respective solutions for 100seconds. Thereafter, the solutions were removed, and the lumens wereperfused according to the continuous perfusion method discussed above.

On the eighth day, the catheters were disconnected and susceptibility tomicrobial adherence was evaluated. The distal lumens of each group ofcatheters were separately filled with the following amounts of bacteria(S. aureus, P, aeruginosa, and Enterobacter) or yeast (C. albicans):

(1) 8×10⁸ CFU/ml culture of S. aureus;

(2) 8×10⁶ CFU/ml culture of P. aeruginosa;

(3) 8×10⁸ CFU/ml culture of Enterobacter; and

(4) 8×10⁶ CFU/ml culture of C. albicans.

The four subgroups of lumens were prepared for evaluating microbialadherence to the catheter lumens as described above. The ends of thecatheters were heat sealed, incubated, subcultured, externallysterilized, flushed, subdivided, placed in inactivating media andsonicated according to the techniques set forth supra. Thereafter, 0.5ml of the extract was subcultured, incubated and examined to determinethe colony counts. The results are shown below in Table 2.

TABLE 2 Adherence of Adherence of Adherence of Adherence of S. aureus P.aeruginosa Enterobacter C. albicans Solution (CFU/cm) (CFU/cm) (CFU/cm)(CFU/cm) 80% (v/v) 1.3 × 10⁴ >10⁵ >10⁵ 1.7 × 10⁴ reagent alcohol + 20%(v/v) THF 1.2% CHX + 3 9 2 26 1.2% CHA in 80% (v/v) reagent alcohol +20% (v/v) THF

The results shown in Table I demonstrate the synergistic antimicrobialeffect of treating a polyurethane central venous catheter lumen with asolution comprising the mixture of CHX and CHA. Table 2 shows thatarticles treated with CHX and CHA exhibit an increased effectivenessacross a wide variety of organisms by decreasing luminal adherencesubstantially more than articles treated with no antimicrobial agents.

In a further study, the luminal surface of three groups of otherwiseidentical polyurethane central venous catheters were separately treatedwith one of the following three solutions:

(1) 2% CHA in a solvent system of 80% (v/v) ethanol and 20% (v/v) THF;

(2) 0.625% CHX and 1.375% CHA in a solvent system of 80% (v/v) ethanolplus 20% (v/v) THF; and

(3) 1% CHX and 1% CHA in a solvent system of 80% (v/v) ethanol plus 20%(v/v) THF.

The solution was pushed into the lumen and allowed to remain for 100seconds.

The amount of uptake of chlorhexidine in the catheters was determinedusing a spectrophotometric method after extraction with alcohol.

In order to determine the amount of drug retention and antimicrobialefficacy, the catheters were perfused for 6 days with 1.500 L of salineper day. The treated catheters were then studied on Day 1 and Day 6after perfusion to determine the amount of drug retention. Thechlorhexidine in the catheter after perfusion was determined using aspectrophotometric method after extraction with alcohol. Theantibacterial activity was measured on Day 6 after perfusion by countingthe CFU/cm of S. epidermidis. Table 3 shows results of the uptake, drugretention and antibacterial activity of the treated catheters.

TABLE 3 Antibacterial Retention of Drug Activity (CFU/cm) Uptake (μg/cm)S. epidermidis Solution (μg/cm) Day 1 Day 6 Day 6 2% CHA in 44 34 8 10²80% (v/v) Ethanol + 20% (v/v) THF 0.625% CHX + 70 43 22 0 1.375% CHA in80% (v/v) Ethanol + 20% (v/v) THF 1% CHX + 80 45 26 0 1% CHA in 80%(v/v) Ethanol + 20% (v/v) THF

These results demonstrate the synergistic antimicrobial effect oftreating a polyurethane central venous catheter lumen with a solutioncomprising a mixture of CHX and CHA.

5.2 EXAMPLE Urinary Catheters

Hydrophilic urinary catheters were separated into two otherwiseidentical groups, and the whole catheters (i.e., external and luminalsurfaces of the catheter) were treated with a solution containingeither:

(1) 4% CHA in a solvent system of 85% (v/v) THF and 15% (v/v) methanol;or

(2) 2% CHX plus 2% CHA in a solvent system of 85% (v/v) THF and 15%(v/v) methanol.

The catheters of each group were soaked in the respective solution for30 minutes to one hour. Thereafter, the catheters were removed from thesolution.

The amount of uptake of chlorhexidine was determined using aspectrophotometric method after extraction with alcohol, which resultsare shown below in Table 4.

The two groups of catheters were separately exposed to cultures of P.aeruginosa and C. albicans in order to study the antimicrobial efficacyof the medical article. Trypticase soy agar plates were seeded with 0.3ml of 10⁸ CFU/ml of P. aeruginosa and C. albicans, respectively.Thereafter, a 0.5 cm length of urinary catheter was placed on each platewith three units per plate. The plates were then incubated for 24 hoursat 37° C. After 24 hours, the zones of inhibition were measured forDay 1. To measure the zones of inhibition for Day 2 to Day 6, theprocess was repeated upon transferring the units to fresh agar platessimilarly prepared. The results are shown in Table 4.

TABLE 4 Antimicrobial Efficacy Antimicrobial Efficacy (Zone ofInhibition (Zone of Inhibition (mm)) P. aeruginosa (mm)) C. albicansUptake Day Day Solution (μg/cm) 1 2 3 4 5 6 1 2 3 4 5 6 4% CHA in 123 1511 10 9 0 0 11 9 0 0 0 0 85% (v/v) THF + 15% (v/v) Methanol 2% CHX + 38016 13 11 10 10 10 12 11 11 10 9 6 2% CHA in 85% (v/v) THF + 15% (v/v)Methanol

These results demonstrate the synergistic antimicrobial effect oftreating the urinary catheters with a solution comprising a mixture ofCHX and CHA.

5.3 EXAMPLE PTFE Soft Tissue Patches

Disks cut from PTFE soft tissue patches, which are hydrophobic polymericmedical articles, were treated with a solution that contained CHA aloneand a solution that contained a CHX—CHA complex in accordance with thepresent invention. Groups of disks having a 1 mm thickness were treatedfor one hour with one of the following solutions:

(1) 0.4% CHA in a solvent system of 70% (vlv) THF and 30% (v/v)methanol; or

(2) 0.2% CHX and 0.2% CHA in a solvent system of 70% (vlv) THF and 30%(v/v) methanol.

The amount of uptake of chlorhexidine in the PTFE disks was determinedusing a spectrophotometric method after extraction with alcohol, and theresults are shown below in Table 5.

The two groups of disks were separately exposed to cultures of P.aeruginosa and S. epidermidis in order to study their antimicrobialefficacy. Trypticase soy agar plates were seeded with 0.3 nil of 10⁸CFU/ml of P. aeruginosa and C. albicans, respectively. Thereafter, 0.5cm diameter disks were placed on each plate with three units per plate.The plates were then incubated for 24 hours at 37° C. After 24 hours,the zones of inhibition were measured for Day 1. The process wasrepeated upon transferring the disks to fresh agar plates similarlyprepared for Day 2 to Day 6. The zones of inhibition are shown in Table5.

TABLE 5 Antimicrobial Efficacy Antimicrobial Efficacy (Zone ofInhibition (Zone of Inhibition (mm)) P. aeruginosa (mm)) S. epidermidisUptake Day Day Solution (μg/cm) 1 2 3 4 1 2 3 4 0.4% CHA in 450 8 5 0 012 10 9 9 70% (v/v) THF + 30% (v/v) Methanol 0.2% CHX + 840 12 8 8 7 1513 12 11 0.2% CHA in 70% (v/v) THF + 30% (v/v) Methanol

These results demonstrate the synergistic effect of treating PTFE softtissue patches with a solution comprising a mixture of CHX and CHA.

Bacterial adherence on PTFE soft tissue patch disks treated with CHAalone, CHX alone, or a mixture of CHA and CHX were studied. 2 mm thickdisks were separated into four groups and separately treated with one ofthe following solutions:

(1) a solvent system of 70% (vlv) THF and 30% (v/v) methanol with noantimicrobial;

(2) 0.4% CHA in a solvent system of 70% (v/v) THF and 30% (vlv)methanol;

(3) 0.4% CHX in a solvent system of 70% (v/v) THF and 30% (v/v)methanol; and

(4) 0.2% CHX and 0.2% CHA in a solvent system of 70% (v/v) THF and 30%(v/v) methanol.

In order to determine the bacterial adherence to the PTFE, three disksof 1 cm diameter from patches in each treatment group were soaked andagitated in 3.0 ml of media containing 50% (v/v) bovine adult serum and50% (v/v) trypticase soy broth. The media was changed on days 1, 2 and4. On the fourth day, 10⁵ CFU/mI of S. aureus was added to the media. Onthe fifth day after agitation in media, the disks were removed, rinsedand rolled on to plates of drug inactivation agar. The plates were thenincubated for 24 hours at 37° C. Thereafter, the colony counts weredetermined, and the amount of antimicrobial present in the disks wasdetermined by extracting the antimicrobial from the disk with alcohol,followed by spectrophotometric measurement. The results are shown inTable 6.

TABLE 6 Bacterial Adherence of Drug levels S. aureus (CFU/cm) Solution(μg/disk) Day 5 70% (v/v) 0 >10⁵ THF + 30% (v/v) methanol 0.4% CHA in264 8 × 10² 70% (v/v) THF + 30% (v/v) methanol 0.4% CHX in 361 1 × 10²70% (v/v) THF + 30% (v/v) methanol 0.2% CHA + 360 60 0.2% CHX in 70%(v/v) THF + 30% (v/v) methanol

These results demonstrate the synergistic effect of treating PTFE softtissue patches with a solution comprising a mixture of CHX and CHA.

Various publications are cited herein, which are hereby incorporated byreference in their entireties.

1. An antimicrobial medical article prepared by treating a hydrophobicpolymeric medical article, for an effective period of time, with asolution consisting essentially of one or more solvents and a mixture ofchlorhexidine free base and a water-soluble chlorhexidine salt, whereinthe weight/weight ratio of chlorhexidine free base and the water-solublechlorhexidine salt in the solution is between 1:1 to 1:5. 2-14.(canceled)
 15. The antimicrobial medical article of claim 1, wherein thearticle is expanded polytetrafluoroethylene.
 16. The antimicrobialmedical article of claim 1, wherein the article is apolytetrafluoroethylene soft tissue patch. 17-20. (canceled)
 21. Amethod of preparing a medical article comprising the steps of: (i)placing the medical article in a solution consisting essentially of (a)a solvent selected from the group consisting of water, reagent alcohol,tetrahydrofuran, dimethylsulfoxide, dimethylformamide,N-methyl-2-pyrrolidone, and mixtures thereof; and (b) a mixture ofchlorhexidine free base and a water-soluble chlorhexidine salt, whereinthe weight/weight ratio of chlorhexidine free base and water-solublechlorhexidine salt in the solution is between 1:1 to 1:5; (ii) soakingthe medical article in the solution for an effective period of time toallow the medical article to swell; (iii) removing the medical articlefrom the solution; and (iv) drying the medical article.
 22. (canceled)23. The method of claim 21, wherein the medical article is a hydrophobicpolymeric medical article.
 24. The method of claim 23, wherein thehydrophobic polymeric medical article is selected from the groupconsisting of expanded polytetrafluoroethylene and apolytetrafluoroethylene soft tissue patch.
 25. An antimicrobial medicalarticle prepared by treating a medical article, for an effective periodof time, with a solution comprising a solvent and an antimicrobialmixture consisting essentially of chlorhexidine free base and awater-soluble chlorhexidine salt, wherein the molar ratio ofchlorhexidine free base and the water-soluble chlorhexidine salt in thesolution is between 1:1 and 1:5.
 26. The antimicrobial medical articleof claim 25, wherein the article is a catheter.
 27. The antimicrobialmedical article of claim 25, wherein the article is a hydrophobicpolymeric medical article.
 28. The antimicrobial medical article ofclaim 27, wherein the hydrophobic polymeric medical article is selectedfrom the group consisting of expanded polytetrafluoroethylene and apolytetrafluoroethylene soft tissue patch.